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SAE 2600 restoration/recap.....need assistance.

There are resistors in the pre-driver section that need to be closely matched. You might as well go 1% metal film when replacing the resistors. I think the schematic specifies that the originals are all 1/3w or larger.
 
Okay, I will do all of that. Yes,I too am sure a great deal in this amp has been thermally stressed. I can see three different stickers on the back from repair shops with dates and short descriptions of work done.
 
FootFungus said:
There are resistors in the pre-driver section that need to be closely matched. You might as well go 1% metal film when replacing the resistors. I think the schematic specifies that the originals are all 1/3w or larger.
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I think you are correct, in the bad schematics I have I can see a note that says all resistors 1/3w unless otherwise noted. I might as well order several resistors of each and pick out the best matched.
 
There is a lot of work in that amp. It was top of the line and very fine sounding. Definately worth the trouble. Contact me if you need the bias IC. I may have a few in my parts box.
 
grateful said:
There is a lot of work in that amp. It was top of the line and very fine sounding. Definately worth the trouble. Contact me if you need the bias IC. I may have a few in my parts box.
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Thanks! If I need that I'll contact you.:yes:
 
Resistors on the driver boards: I usually leave them alone unless there are signs of thermal damage. You can also check resistance of each resistor "in circuit" and compare values for the left and right channel. If values are very different, desolder one leg of the resistor, lift it and re-measure value. Change if out of spec, in both channels.

Sometimes I change input resistors if they are 5% carbon to Vishay metal film 1% in the belief it change sound and reduce noise.

Change electrolytic caps; I usually do not change ceramics. If you find some tantalium caps, change them to polypropylene or electrolytes.

Check ALL boards for cold joints especially if you had overheating problems.

Rob41 said:
Thank you kotofei, I will follow your suggestions. Resistors are cheap and I really just want to do this right so it lasts for many years to come.

Should all of the resistors be changed on the driver boards as well? While we're at it, I've heard there is usually no reason to change the little ceramic disc caps. Does anyone change them anyway while they are doing the work or would that be totally unnecessary?
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Thanks for the tips. Although I had to look up a picture of a tantalium cap, I'm upto speed now.
 
Just ordered 8 MJ21194G and 8 MJ21193G output transistors from Mouser along with a few more caps and resistors. I'm sure there will be at least another order in the 26oo's future. Tomorrow while out of town I'll be able to pick up some solder and a new solder sucker. As soon as some of the parts arrive I'll be able to start the work in earnest.
 
Get a handheld solder pump. Cost approx $5 in the Ebay. Helps A LOT in projects like this.
 
price no object as long as it didn't go over.

I would say that the entire circuit may be described as cost effective to a point. Components were figured to the penny and applied accordingly. The circuit was never expected to perform beyond final assembly.
This idea is rampant in the US industry. Very little concern for age of components.
It may have been what brought down the auto industry.

Paul
 
ryuuoh said:
A worthy investment might be a Hakko 808:
http://www.amazon.com/Hakko-Desoldering-Kit-With-808/dp/B000ARPULW
I love mine. Very effective and fast.
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Looks great but my checkbook won't like that right now. Maybe by summer one of those will be in the cards.

kotofei said:
Get a handheld solder pump. Cost approx $5 in the Ebay. Helps A LOT in projects like this.
Click to expand...

I picked up a solder sucker from Rat Shack today along with a few other minor tools and new fasteners for the output transistors that are on the way.

I was able to find several PDF scans from the SAE 2500/2600 service manual which is making my job much easier and the schematics should be along soon as well. Below is the PDF of both the Drive board and the Pre-Drive boards.
 

Attachments

I found a bag of Bergquist K-10 sil-pads I bought last year. I would like to use these but need to know if I still need to use thermal grease on them?

Also, when I removed the part of the heat sink they are mounted in I saw a great deal of almost runny thermal grease between the heat sink pieces. So much so that it is filling almost all of the holes for the transistors. Should it be like that? Should thermal grease be all over the transistor pins?

If I need to apply thermal grease to the sil-pads and between heatsink parts, what t-grease should I use? Does Mouser carry the correct type?

edit: Just to be clear, there was white paste on both sides of the old mica pads. The other grease between heat sink parts and in the transistor holes was a clear silicone looking substance.
 
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The Silpads don't need grease. Go ahead and clean out all the gunk you can in the pin and heatsink holes if you haven't already.
 
FootFungus said:
The Silpads don't need grease. Go ahead and clean out all the gunk you can in the pin and heatsink holes if you haven't already.
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Alright, sounds good. What about using a thermally conductive compound between the heat sink plates? If I need something there is there a product that won't run all over like the last stuff did? I know the old stuff was some kind of silicone product a repairman had used but it sure seemed to run everywhere.
 
You could use a thin coat of regular ceramic heat sink compound for the heat sinks. That is what was on my Sansui 9090.
 
Watching with interest and to learn. Got a couple amps I need to go through. Steady as she goes Rob!! :lurk:
 
ryuuoh said:
You could use a thin coat of regular ceramic heat sink compound for the heat sinks. That is what was on my Sansui 9090.
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Thanks, I will do that.

GoRNR said:
Watching with interest and to learn. Got a couple amps I need to go through. Steady as she goes Rob!! :lurk:
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Trust me when I tell you I am learning a great deal as I proceed. I'm an Engineer on a ship so I amused to working on many things I have had no previous experience working on and do a lot of trouble shooting. Electrical equipment is a big part of it but not so much with electronics. We usually follow a T/S guide to determine which board needs replacing rather than repairing individual components. On my ship we generate AC voltage and run it through line filters and SCR's that fill a small room so we can provide DC the 600VDC main motors. We routinely change out $5k to $15k cards and it makes me cringe. I look at them and see not one expensive component on them.
 
I have just run into a stumbling block. There are no less than four different pairs of devices on the Driver and Pre-driver cards. There is only supposed to be one number for the NPN's and one number for the PNP's. Only one P/N is used for each type on all four cards.

Of the devices that still bear the SAE number I tried to cross them at Wardsweb and wouldn't you know it, there is no cross information for either of them. Okay, so I have a few other numbers from the other devices and I look up the data sheets but I don't what to look for and I really don't know which ones would be correct either.

Left Driver---C2238 and A968----clearly not original---Good replacement?

Right Driver---RCA 8323 and RCA 8327----also not original---Good replacement?

Left Pre-Driver---Nec 2336 and ???

Right Pre-Driver---2N6211 and 11-0066B(SAE number)

I would like to know what to look for in the data sheets to see if these are even equivalents or not. I think it may be in my best interest to buy new devices for all four cards. It's just a matter of figuring out which devices to get. :scratch2:

edit: To add to the confusion, a man in Japan who did a really nice rebuild of one of these has the device 66566 on a couple of his boards.
 
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